Undesirable moisture, particularly in fuels such as diesels and biodiesels, continues to be a widespread issue in the fuel industry. Moisture can cause many problems in fuel-dependent operations, including inducing corrosion, accelerating fuel breakdown and oxidation speed, and reducing the lifespan of equipment that burns the fuel.
Governments and corporations are pushing for a greater percentage of liquid fuels to be manufactured from non-fossil fuel based feedstocks to take advantage of lessened carbon and nitrogen oxide emissions that are associated with such fuels. Fuel feedstocks may also be grown “in-country”, which mitigates a country's reliance on foreign oil deposits to meet national fuel demands and enables better control over pricing.
However, bio-based fuels are substantially more susceptible to hygroscopic absorption of moisture than traditional hydrocarbon-based fuels, resulting in an increased amount of moisture absorbed and stored in the bio-fuel. The moisture that accumulates is particularly problematic as it cultivates the growth and proliferation of undesirable bacteria, yeast, fungi, and mould in the fuel. These organisms, in conjunction with the elevated moisture levels, can cause common corrosion, microbially induced corrosion, elevated acidity levels in-fuel and in-tank, reduction of lubricity, and accelerated fuel breakdown, all of which also reduce the operating lifespan of the equipment utilizing the fuel.
High moisture levels in diesel fuels may further cause mechanical injector failure in engines as moisture present in the fuel expands at a higher rate than the fuel it is being carried with when both are introduced into the high heat of a combustion chamber. Moisture in the combustion chamber turns to steam, expands rapidly, and may cause damage to the injector tips, or parts thereof, leading to injector failure, rough engine idling, reduced engine performance, reduced fuel economy, and, in extreme conditions, may even flood the combustion chamber with fuel causing possible catastrophic detonation.
A number of methods have been proposed in the fuel processing, handling, shipping, storage and management industries to remove or separate moisture from fuels. The methods that have been proposed include filtration with a coalescing or absorptive style media, centrifugal separation by molecular weight, temperature increase separation, temperature decrease separation, and aeration with associated dehydration.
The methods of moisture removal or separation that have hereto been proposed are expensive, time consuming, and inefficient. For example, methods of removing moisture from fuel that include excessive heating of the fuel can lead to oxidation, which causes breakdown of the fuel, induces precipitate formation, causes fuel/fluid chemical instability, and decreases the lifespan of the fuel. Further, heating a fuel causes it to “off-gas” near its regular flash point (many diesel fuels have a flashpoint near 52 degrees Celsius and almost all have a flashpoint lower than 60 degrees Celsius, unless they have been mixed, for example, as bunker fuel for ships), which makes the atmosphere around the fuel prone to combustion. As another example, methods that utilize freezing often keep the fuel cloudy after it is returned to room temperature as it is difficult to obtain a moisture level that is below 200 ppm with such a process. In general, methods that can be performed at room temperature are preferred as they avoid the above noted problems.
As a further example, coalescing, “stripping” or “wicking” style filtration media, and certain centrifuge water separation technologies, work on the basis of water droplet size and surface tension differentials. These methods often become ineffective as moisture is absorbed into bio-fuels and the mixture becomes a true solution, or for a chemically bonded emulsion. As the differential surface tension between the moisture and the fuel is reduced, moisture can no longer be “detected” by the coalescing media as distinct and separate from the fuel and passes through the filtration technology along with the fuel. Few of the proposed methods of fuel dehydration can remove absorbed or long term finely emulsified and chemically bonded water from fuels, oils or other hydrocarbon-based fuels and none can do so in an efficient and cost effective manner.
What is required is a new and efficient method of dehydrating fuel, specifically bio-diesel, that mitigates the drawbacks of current dehydrating technologies.